Deriving tropical gynoecious inbred backcross lines from exotic pickling cucumber using marker assisted backcross breeding

Abstract

Indian cucumber cultivars are basically monoecious and vigorous in nature with many lateral branches but they are poor in productivity. The present study was aimed to introgress gynoecious trait (F locus) from pickling cucumber line (Gy14) into elite Indian cultivar Pusa Uday using marker assisted backcross breeding. Based on allelic diversity analysis, the allele numbers per locus ranged from 2 to 3 in BC1F3 and the observed heterozygosity (Ho) was ranged from 0.01 to 0.55. The heterozygosity expected (He) mean was 0.28 (range 0.03 to 0.50) which was higher than mean Ho (0.18) and mean polymorphic information content (PIC) for 87 markers was 0.23. Whereas the allele numbers per locus was 2 in BC2F2 and the observed heterozygosity (Ho) was ranged from 0.01 to 0.56. The mean expected heterozygosity (He) was 0.24 which was higher than mean Ho (0.17) and the mean PIC value was 0.19. The gynoecism (F locus) was introgressed in the Indian slicing cucumber cv. Pusa Uday though backcross breeding accompanied by foreground and background selections. The foreground selection was performed with one dominant SCAR marker, and 3 SSR markers (SSR 00233, SSR 15516 and SSR13251). A total of 87 polymorphic markers spanning genetic distance of 1031 cM with an average distance of 12.9 cM between adjacent markers were used for background selection. The genome recovery of the individuals in BC1F3 population was ranged from 62.64% to 93.10% while among BC2F2 plants it was ranged from 89.66% to 95.40%. Four inbred backcross lines (IBL) were selected from backcross populations (BC1F4 and BC2F3) those were purely gynoecious even at 45°C with more than 5 lateral branches. Hence, marker assisted backcross breeding served as a potential approach for precise introgression of the gynoecy (F locus) from picking cucumber to Indian slicing cucumber.